U.S. patent number 7,307,791 [Application Number 10/906,360] was granted by the patent office on 2007-12-11 for head mounted device.
This patent grant is currently assigned to Himax Technologies Limited. Invention is credited to Kuo-Yuin Li, Chia-Fen Lin.
United States Patent |
7,307,791 |
Li , et al. |
December 11, 2007 |
Head mounted device
Abstract
A head-mounted display (HMD) comprises a frame for hanging on a
user's head, and a display device affixed to the frame. The display
device comprises alight source, a driving circuit for generating
data signals, a polarization beam splitter (PBS), for passing the
light emitted from the light source, a liquid crystal on silicon
panel (LCOS panel) for reflecting the light from the PBS based on
the data signal generated by the driving circuit, and a lens group
including a biconvex glass spherical prism and an aspherical
plastic prism. The lens group is used for focusing the reflected
light from the LCOS panel.
Inventors: |
Li; Kuo-Yuin (Tainan County,
TW), Lin; Chia-Fen (Tainan County, TW) |
Assignee: |
Himax Technologies Limited
(Fonghua Village, Sinshih Township, Tainan County,
TW)
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Family
ID: |
36125244 |
Appl.
No.: |
10/906,360 |
Filed: |
February 16, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060072205 A1 |
Apr 6, 2006 |
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Foreign Application Priority Data
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Sep 30, 2004 [TW] |
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93129648 A |
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Current U.S.
Class: |
359/630; 359/649;
359/664; 359/708 |
Current CPC
Class: |
G02B
27/0172 (20130101); G02B 5/30 (20130101); G02B
2027/0178 (20130101) |
Current International
Class: |
G02B
27/14 (20060101) |
Field of
Search: |
;359/630,649,664,708 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dang; Hung X.
Assistant Examiner: Martinez; Joseph
Attorney, Agent or Firm: Hsu; Winston
Claims
What is claimed is:
1. A display apparatus comprising: an image generation device; and
a lens group consisting of a biconvex spherical prism and an
aspherical prism, the lens group being used for focusing a light
from the image generation device, wherein the light from the image
generation device does not pass through any other lenses before
entering the lens group.
2. The display apparatus of claim 1, wherein the biconvex spherical
prism is made of glass and the aspherical prism is made of
plastic.
3. The display apparatus of claim 1, wherein the aspherical prism
is substantially adhered to the biconvex spherical prism.
4. The display apparatus of claim 1, wherein the aspherical prism
is a concave-convex prism.
5. The display apparatus of claim 4, wherein a conical coefficient
of the concave surface of the aspherical prism is in a range
between 0 and 1, and a conical coefficient of the convex surface of
the aspherical prism is in a range between -0.3 and -500.
6. The display apparatus of claim 4, wherein a dispersive power of
the biconvex spherical prism is substantially in a range between 60
and 65.
7. The display apparatus of claim 1, wherein the image generation
device is a liquid crystal on silicon panel (LCOS panel), and the
LCOS panel comprising a color filter.
8. The display apparatus of claim 1, further comprising a
polarization beam splitter for passing the light from the image
generation device to the lens group.
9. The display apparatus of claim 1, further comprising: a light
source for emitting the light; and a polarization beam splitter for
directing the light to the image generation device and passing the
light reflected from the image generation device to the lens group.
Description
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a head mounted device, and more
particularly, to a head mounted device utilizing an LCD panel.
2. Description of the Prior Art
A head-mounted display (HMD), a three-dimensional visual optical
device, is the first device providing its wearer with an immersive
experience. The typical HMD houses two miniature display screens
and an optical system that channels the images from the screens to
the eyes, thereby presenting a stereo view of a virtual world.
Recently, the head mounted display as an input apparatus in
response to a user's action is widely utilized in an augmented
reality or a virtual reality system. Continuously measuring the
position and orientation of the user's head by means of a motion
tracker allows an image generating computer to adjust a scene
representation to a current view. As a result, the viewer can look
around and walk through the surrounding virtual environment. In
addition, text and images can be projected on a screen for viewing
by the user therefore realizing an augmented reality or a virtual
reality environment.
The HMD utilizes a lens group to enlarge an image generated by a
small 2-dimension Liquid Crystal Display (LCD). In detail, the
image generated by the small liquid crystal display and through the
lens group having prisms with decentration free-form surface can be
projected on the pupil of the user which sees an enlarged
projection image. Such an effect is called a hologram.
The conventional head mounted display fails to gain popularity due
to its large volume, heavy weight, and expensive price.
Accordingly, smaller volume, less weight, and lower price will be
key factors to entice consumers to purchase a new head mounted
display.
SUMMARY OF INVENTION
Briefly summarized, the claimed invention provides a head-mounted
display (HMD) comprising a frame for hanging on a user's head and a
display device affixed to the frame. The display device comprises a
light source, a driving circuit for generating data signals, a
polarization beam splitter (PBS) for passing the light emitted from
the light source, a liquid crystal on silicon panel (LCOS panel)
for reflecting the light from the PBS based on the data signal
generated by the driving circuit, and a lens group including a
biconvex glass spherical prism and an aspherical plastic prism, the
lens group being utilized for focusing the reflected light from the
LCOS panel.
According to the claimed invention, a display apparatus comprises
an image generation device, and a lens group faced against the
image generation device consisting of a biconvex spherical prism
and an aspherical prism.
According to the claimed invention, a display apparatus comprises
an image generation device, a lens group faced against the image
generation device including a biconvex spherical prism and an
aspherical prism, and a polarization beam splitter (PBS) disposed
adjacent to the image generation device and the lens group.
These and other objectives of the present invention will no doubt
become obvious to those of ordinary skill in the art after reading
the following detailed description of the preferred embodiment that
is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows an optical display system having a head-mounted
display and a control system according to the present
invention.
FIG. 2 shows a block diagram of the head mounted display.
FIG. 3 shows another embodiment according to the present
invention.
DETAILED DESCRIPTION
Please refer to FIG. 1, which shows an optical display system 100
having a head-mounted display 10 and a control system 15 according
to the present invention. The user wears the head-mounted display
10 and can see vivid images through the display device 14 affixed
to the frame 12 in response to the control system 15. The control
system 15 is wirelessly connected or is wired-connected with the
head-mounted display 10 by means of a transmission line 16.
Please refer to FIG. 2, which shows a block diagram of the head
mounted display 10. The display device 14 contains a lamp 20, a
display driver 22, a liquid crystal on silicon (LCOS) panel 24, a
polarization beam splitter (PBS) 26, and a lens group 30. Light
emitted from the lamp 20 travels through the polarization beam
splitter (PBS) 26 and reflects the S-type polarization light to the
LCOS panel 24. The LCOS panel 24 modulates the received S-type
polarization light into P-type polarization light based on a
control signal from the display driver 22, which is controlled by
the control system 15. The modulated P-type polarization light
passes through the PBS 26 and is directed by the lens group 30 to
the pupil of the user; who sees an enlarged image. In other words,
the function of the PBS 26 is utilized to allow both the light from
the LCOS panel 24 and the ambient light from the user's surrounding
environment to enter the user's pupil. As a result, the user with
the optical display system 100 can see the real surroundings
overlapping with a virtual image which is generated by the LCOS
panel 24 based on the signal from the display driver 22 which is
controlled by the control system 15. The PBS 26 is disposed
adjacent to a lens group 30 and the LCOS panel 24. The lens 30 is
used for adjusting the focus length of the incident light reflected
from the LCOS panel 24. The proper focus length named as an eye
relief d affects the comfortable visible distance. The comfort of
the user's view will increase as the eye relief d value (i.e.,
distance) increases. Moreover, a display apparatus has two display
devices 14, each located in front of left and right eyes of the
user. The two display devices 14 are utilized to generate a stereo
image effect. The LCOS panel 24 comprises a color filter to filter
incident light. The color or colors of the color filter may be
selected from the group consisting of red color, green color, blue
color, or any combination thereof.
The lens group 30 comprises a biconvex glass prism 32 and an
aspherical plastic prism 34, which is a concave-convex prism, and
the biconvex glass prism 32 is adhered to the aspherical plastic
prism 34.
Light that travels through a single spherical prism tends to
exhibit a pincushion distortion image. One way to solve such
pincushion distortion phenomenon problem is to increase a number of
spherical prisms to modify the distortion phenomenon, however, this
solution increases the total weight and volume of the lens group
30. As a result, in this embodiment, only a single aspherical prism
and a single spherical prism are utilized instead of multiple
prisms to form the lens group 30. A proper aspherical prism can
improve spherical aberration and promote improved image quality.
Furthermore, decreasing the number of prisms can reduce
manufacturing cost and meet a HMD 10 requirement of light and
small.
In addition, material of prisms affects focus effect. At present,
the widely utilized optical prisms are typically made of glass or
plastic. The glass prism, in comparison to the plastic prism, has a
lower temperature coefficient, a higher transmittance, and a higher
melting point. The higher temperature coefficient indicates that
molecules of the glass prism are prone to vary (e.g., refraction
power and focus length of the prism may change) under high
temperature difference environments. However, more time is required
to polish the prism and costs are greater resulting in degraded
yield and capacity of manufacturing the prisms. Considering the
glass prism made of high purity synthetic resin with higher
temperature coefficient and lower melting point, these are suitable
for mass production by injection molding. In addition, the plastic
prism compared to the glass prism, has the feature of lower cost
and weight.
The aspherical prism is made of plastic and the spherical prism is
made of plastic. A reflectance of the biconvex of the spherical
prism is substantially in a range between 1.50 and 1.60. The
dispersion power of the biconvex of the spherical prism is
substantially in a range between 60 and 65. A conical coefficient
of the concave surface of the aspherical plastic prism is in a
range between 0 and 1, and a conical coefficient of the convex
surface of the aspherical plastic prism is in a range between -0.3
and -500.
FIG. 3 shows another embodiment of present invention. Meanwhile, in
FIG. 3 a device same as in or equivalent to FIG. 2 will be
appending a same symbol. The difference between FIG. 2 and FIG. 3
is arrangement of PBS 27 and the LCOS panel 24. Light emitted from
the lamp 20 travels through the PBS 27 and passes through the
S-type polarization light to the LCOS panel 24. The LCOS panel 24
modulates the received S-type polarization light into P-type
polarization light. The modulated P-type polarization light is
reflected by the PBS 27 and is directed by the lens group 30 to the
pupil of the user.
In contrast to prior art, the present invention head mounted
display has a lens group consisting of a biconvex glass spherical
prism and an aspherical plastic prism. An advantage of utilizing
the aspherical is to reduce weight. However, the utilization of an
aspherical plastic prism makes it possible to simplify the
structure, reduce a utilization number of prisms, and reduce the
cost, thereby constructing a lightweight HMD. Moreover, the glass
prism with high refraction power and low dispersive power in
conjunction with an aspherical prism can improve chromatic
aberrations and image quality. In addition, an improvement of
decentration aberration is obtained by enlarging a diameter of an
aspherical prism.
Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
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